Читать книгу Encyclopedia of Renewable Energy - James Speight G., James G. Speight - Страница 56

Biomass power plant emissions will be different from emissions form a coal-based power plant because biomass is lower in sulfur than most US coals. Typical biomass contains 0.05 to 0.20% w/w sulfur on a dry basis. In comparison, coal has 2 to 3% w/w sulfur on a dry basis. The biomass sulfur content translates to approximately 0.12 to 0.50 lb SO₂/MMBtu. Because of this, burning biomass to generate power typically produces less SO₂ emissions than using coal.

NOx emissions should usually be lower for biomass than for coal, due to lower fuel nitrogen (N) content and due to the higher volatile fraction of biomass versus coal. However, this difference may not have much influence on the selection of the technology (i.e., coal or biomass) because the compliance costs are relatively insignificant given the small difference in NOx emissions.

Biomass power production can result in large emissions of carbon dioxide (CO2). Sometimes, biomass combustion results in larger emission values than for fossil fuels because of the lower combustion efficiencies. However, because the carbon dioxide released by combustion was removed from the atmosphere in the recent past through photosynthesis and new plant growth will continue to remove carbon dioxide from the atmosphere after biomass is harvested, it is sometimes argued that biomass is carbon dioxide neutral.

However, in practice, the issue is more complicated since other carbon flows are involved, including carbon dioxide emissions associated with fossil fuel used in harvesting, processing, and transportation operations. Although it is certain that the net amount of carbon dioxide emitted from a biomass power plant is less than a fossil power plant, it must be recognized that under current production practices, biomass power is not a net zero carbon dioxide process.

Biomass combustion device emissions are estimated on a site-specific basis to determine whether a particular location is appropriate for developing a facility. In many cases, data specific to a particular wood-burning appliance are not readily available. However, the United States Environmental Protection Agency provides emission factors that can be used to estimate emissions from wood-fired boilers as part of efforts to estimate the effects of specific combustion sources and determine the applicability of relevant permitting programs.

See also: Acid Rain, Air Emissions.